Cathode ray tuning indicator tube



F. H. BITTER ET AL CATHODE RAY TUNING INDICATOR TUBE April 1, 1958 'Filed Feb. 4, 1953 INVENTOR FRANZ HERMANN BITTER KARL AUGUST BISTERFELD AGENT 2,829,294 CATHODE RAY TUNING INDICATOR TUBE.

Franz Hermann Bitter, Sao Paulo, Brazil, and Karl August Bisterfeld, Hamburg, Germany, assignors, by .mesne assignments, to North American Philips Company, Inc., New York, N. Y., a corporation of Delaware Application February 4, 1953, Serial No. 335,146 Claims priority, application Germany April 26, 1952 1 Claim. (Cl. 313-1075) pled directly to the deflection means and which may be I provided in the same bulb. Such cathode-ray tubes may be used for the substantially powerless indication of voltages, more particularly in the form of zero-voltage indicators or the'like. As an alternative, they may serve for the indication of tuning in amplitude-modulated and frequency-modulated receivers in such manner as to permit indication of tuning either for the two kinds of modulation or in frequency-modulated receivers only.

Cathode-ray tubes for voltage indication comprising two cathode-ray beams are known per se. However, the use thereof involves the disadvantage that the zero-point of the indication is dependent upon influences which can diflicultly be controlled, for example electric or magnetic fields. Marking of the zero position on the luminescent screen thus always involves a certain insecurity.

The present invention avoids the above-mentioned disadvantages and is characterised by two cathode-ray beams emanating from the same cathode and directed substantially diametrically, which beams are each subject, independently of one another, to the action of a pair of deflection means, producing two different luminous indications relatively comparablev and independent of one another, on a luminescent screen which exhibits anode potential and which is arranged at an angle with the direction of the ray.

A cathode-ray tube for the tuning indication according to the invention may alternatively be so constructed that one pair of deflection means with the associated cathode-ray beam serves for the indication of amplitudemodulated oscillations and the other pair of deflection means with the associated beam serves for the indication of frequency-modulated oscillations.

According to the further invention, such a cathode-ray tube which comprises two approximately diametric cathode-ray beams and a luminescent screen having anode potential and being approximately in the form of an obtuse cone or part of an obtuse cone, a cathode which may axially'extend through this screen, and four deflection means between cathode and luminescent screen which are provided substantially parallel to the cathode, may be characterised in that three deflection means are connected together and, if desired, to the anode of one amplifying system and the fourth may be connected to the anode of the other amplifying system.

A tuning indicator tube according to the invention may furthermore comprise a luminescent screen having anode potential and being approximately in the form of an obtuse cone or part of an obtuse cone, a cathode which may axially extend through this screen, and four deflection means between cathode and luminescent screen which areprovided substantially parallel to thecathode,

screen having anode potential and being substantially in the form of an obtuse cone, a cathode axially extend ing through this screen, and four deflection means between cathode and luminescent screen which are provided approximately in parallel and divided symmetrically around the cathode, in such manner that two adjacent deflection means areconnected together, and, if desired,

to the anode of one amplifying system.

In order that the invention may be readily carried into effect, it will now be described with reference to the accompanying drawing showing, by way of example,

one embodiment thereof.

Fig. 1 shows the indicator system of a tube according to the invention and Figs. 2, 3 and 4 show some indication images whichv are obtainable therewith.

Fig. 1 shows an indicator system according to the invention, which is partly cut open to show the details.

A helical grid 2 is provided above a cathode 1 of the conventional type in a manner known per se, four control rods 3 being arranged to be evenly divided around the cathode 1. The assembly is surrounded by a funnellike luminescent screen 4, which is internally coated with fluorescent material, an insulating plate 5 of mica or similar material serving as a support for the whole system.

The electrons emanated by the cathode strike the luminescent screen 4, bringing about in known manner luminous sectors which are separated by sector-shaped shadow ranges. The shadow sectors are produced by the control rods 3 in accordance with the potential applied thereto. The helical grid 2 serves in known manner to obtain a virtual cathode having an electron density which is evenly divided over the surface thereof.

If three control rods are connected together and to the anode of an amplifying system (not shown) which is arranged in the same bulb and the control grid of which has supplied to it the amplitude-modulated control voltage, and if the fourth control rod is connected to the anode of a second amplifying systems, which is likewise arranged in the same bulb and the control grid of which has supplied to it a control voltage derived from the discriminator, an indication image is obtained such as shown diagrammatically in Fig. 2. In this case, the upper half of the luminescent screen serves for the frequency-modulation indication and the lower half serves for the amplitude-modulation indication. Fig. 2 shows, at the left, the case in which there is tuned to the lefthand side-band of the carrier wave, in the middle the case of correct tuning to the carrier wave, and at the right the case of tuning to the right-hand side-band of the transmitter to be received. With frequencymodulated waves a luminous sector is obtained, of which the aperture angle is dependent upon the value of the high frequency amplitude and can be proportioned to be comparatively narrow, since this amplitude is substantially constant in the vicinity of the carrier-wave. The luminous sector is vertical with correct tuning, but deflects to one direction or the other in case of incorrect tuning, according to the direction in which the receiver is detuned. The tuning indication with amplitude modulation, which takes place in the lower half of the luminescent screen, gives the usual known image.

If such a tuning indicator tube is to be used only for frequency-modulation reception, the rods 3 may in pairs be interconnected in a crosswise manner and acquire rela- Patented-Apr.- 1, 1958* macaw;

' points of a discriminator circuit, if desired each with the interposition of an amplifying system. In this case, a tuning indication ensues such as shown in Fig. 3. The indication is constituted by two narrow luminous sectors which are in diametrical opposition, the width of the sectors being dependent upon the high frequency-amplitude and hence constant With correct tuning the image shown in the middle is obtained, in which the luminous sectors are positioned vertically, and with tuning to one side-band or the other the luminous rod, constituted by the .two sectors and moving transversely over the luminescent screen, deflects about the centre thereof in one direction of. rotation or the other according to the direction of the variation in tuning. This is clarified by the two positions shown at the right and at the left in Fig. 3. As compared with known devices, this arrangement atl'ords the advantage that the luminous rod is longer than the luminous index in the known devices, so that a clear indication is obtained.

It is inconvenient in this method of indication that for ascertaining correct tuning the indicator tube is required to comprise a mark either indicating the vertical position of the luminous rod or permitting an indication of correct tuning. This disadvantage may be obviated if each two adjacent control rods are interconnected and thus united to form one group. An indication thus ensues such as shown in Fig. 4. In this case also the luminous sectors with correct tuning are positioned vertically, that is to say exactly in diametrical opposition.

4 In case of detuning, both the upper and the lower luminous sectors are deflected to the left or to the right, so that the luminous rod is apparently kinked at its centre. Correct tuning may in this case readily be ascertained without the use of a mark due to the luminous rod appearing straight instead of kinked.

What we claim is;

A cathode-ray tuning indicator device comprising a comically-shaped anode having a fluorescent screen on the interior thereof, a cathode member positioned concentrically within said anode and producing a pair of substantially diametrically directed beams, and four control rods symmetrically surrounding said cathode within said anode, and located at the corners of a square defined thereby, three of said control rods being connected together and insulated from the fourth control rod.

References Cited in the file of this patent UNITED STATES PATENTS 2,051,188 Thompson Aug. 18, 1936 2,105,818 Parker Jan. 18, 1938 2,122,268 Wagner June 28, 1938 2,219,506 Steimel et al Oct. 29, 1940 2,701,319 Coleman Feb. 1, 1955 2,712,612 Lieb July 5, 1955 FOREIGN PATENTS 853,504 France Dec. 7, 1939 721,599 Great Britain Jan. 12, 1955 

